I was reading this review of Henry DAC.
My interest from this unit comes from the fact that unit's schematics and code are open source! IMHO, that is pretty cool.
Sound on the other hand remains to be seen...
And btw, has anyone ever tried this unit? I am seriously considering buying it just to satisfy my curiosity.

Another thing that stuck with me was this claim from the unit designer:

"ESS don't make their products available through typical electronic parts distributors. Getting them in low volumes was a big hassle. But what made me choose another chip was the discovery of an internal math bug in the ES9022/9023. A >-1.3dB full-scale square wave played through their chip will generate great amounts of distortion. With modern compressed music, that isn't just a theoretical occurrence. I worked many years with signal conditioning and was able to see what goes on. In technical terms, the internal FIR filter does a 2's complement overflow where a very positive number actually flips around and becomes a very negative number. This occurs before the sigma-delta modulator. A digital limiter or lower gain in the FIR would solve this."

I do not understand the technicalities of how that works, but it seems like a pretty big oversight from ESS.
And can it really affect music since he mentioned square wave and "great amounts of distortion", and more importantly has someone else noticed this?
Maybe someone with intricate technical knowledge could shed some light on this?

Maybe someone with intricate technical knowledge could shed some light on this?

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It would be unlikely to affect real music. A square wave louder than -1.3db for 16-bit data would be a square wave of maximum level at 0db that is jumping between one exact codeword that represents the minimum (-32767) to another codeword that represents the maximum (32676) in one sample.

This is not going to happen with music. I guess we could in theory see this happen in a brickwalled electroncia recording, but we would probably have much more to worry about than slightly bad math in that case.

There's no replacement for displacement: works for motors, and woofers too.
Portable gear setups in the past 10 years: Sony X to Sony ZX2; UERM to Andro/Solaris. That's it. I don't chase.

Interestingly enough, there is some data about how fast music changes. Way back when, both Nelson Pass and Peter Baxandall looked at this question, and both concluded that the fastest music signal has an equivalent slew rate to a 6 kHz sine wave at full volume. However, in a chapter in the Loudspeaker and Headphone Handbook, Baxandall reported that he had found a music sample that had the equivalent of a 15 kHz sine wave at full volume (close-up recording of drum rim shots, p.154). Given a sampling rate of 44,100 Hz (standard PCM CD rate), this means going from full negative to full positive and back in 3 samples, if I've done the math correctly.

Looks like a balanced tube R2R DAC that uses Analog Devices modules. Not exactly the same ones, but the fact that both Yggdrasil and Gungnir Multibit also use Analog Devices modules crossed my mind. The build sort of reminds me of Lampizators which are also tube R2R DAC's, but the Veridian Utopia appears to be much less expensive (sub-$2K). Unfortunately, there doesn't seem to be many reviews on it.

Looks like a balanced tube R2R DAC that uses Analog Devices modules. Not exactly the same ones, but the fact that both Yggdrasil and Gungnir Multibit also use Analog Devices modules crossed my mind. The build sort of reminds me of Lampizators which are also tube R2R DAC's, but the Veridian Utopia appears to be much less expensive (sub-$2K). Unfortunately, there doesn't seem to be many reviews on it.

Maybe it's a POS like AGD S19, or maybe it could be a hidden gem.

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I don't understand why folks want a tube DAC. The whole point of a DAC is to be 100% transparent, not add "tube character".

Looks like a balanced tube R2R DAC that uses Analog Devices modules. Not exactly the same ones, but the fact that both Yggdrasil and Gungnir Multibit also use Analog Devices modules crossed my mind.

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AD 1865 is a much older (now obsolete) chip, one which is designed for audio, unlike the chips Schiit uses. I think @Hands has heard other NOS DACs based on the same chip, so he might have an idea what to expect.

I don't understand why folks want a tube DAC. The whole point of a DAC is to be 100% transparent, not add "tube character".

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Well, top tier valve DACs can sound exceptionally transparent. It all depends on the glass used. It's not an issue to make a DHT DAC details oriented soundstage monster with texturing and saturation in check, yet not elevated.

Rather than clutter up the forum with yet another thread, I thought I would post some (mostly) brief impressions here. This covers every DAC I have auditioned over the last 9 months, good and bad. Mostly I listened for only 1-2 hrs per DAC, so this is just intended as a rough guide. Prices are UK, before any discount. All using my SPL Phonitor and LCD-XC, except where (noted):

NAD C510, close relative of M51 (£900) [proprietary PWM] - decent bass, notably good on female vocals, only slight sibilance / digitus - much better than Sabres, very good detail. My favourite of all one-bit except maybe DAVE. Volume knob. Possible alternative to Gungnir Multibit if you are in EU and/or don't like Multibit. (2 day A/B vs Yggdrasil) (more)

Rega DAC-R (£600) [2xWM8742] - some bass emphasis / warmth, overall pleasant and smooth sound, resolution not really at the level of C510 or most others. OK if you can get the older version (should sound similar but with inferior USB) used and super cheap, like £100 or £150. Otherwise Modi Multibit is a better deal.

SOtM sHP-100 (£700) [CS4398] - un-fatiguing but very coloured, gooey tone, not much detail/resolution, far behind all including the Rega. Use your laptop or smartphone instead and spend the money on something else.

Rather than clutter up the forum with yet another thread, I thought I would post some (mostly) brief impressions here. This covers every DAC I have auditioned over the last 9 months, good and bad. Mostly I listened for only 1-2 hrs per DAC, so this is just intended as a rough guide. All using my SPL Phonitor and LCD-XC, except where noted:

NAD C510, close relative of M51 [proprietary PWM] - decent bass, notably good on female vocals, only slight sibilance / digitus - much better than Sabres, very good detail. My favourite of all delta-sigma except maybe DAVE. Possible alternative to Gungnir Multibit if you can find it cheaper and/or don't like Multibit. (2 day A/B vs Yggdrasil)

Rega DAC-R [2x WM8742] - some bass emphasis / warmth, overall pleasant and smooth sound, resolution not really at the level of C510 or most others. OK if you can get the older version (should sound similar but with inferior USB) used and super cheap, like £100 or £150. Otherwise Modi Multibit is a better deal.

SOtM sHP-100 [CS4398] - un-fatiguing but very coloured, gooey tone, not much detail/resolution, far behind all including the Rega. Use your laptop or smartphone instead and spend the money on something else.

Price is weighted higher than sound quality in my harshness equation for mediocre/nasty gear. I'm also more likely to call out Benchmark (for example) as a big established manufacturer to bring some balance to the Force. I think this is a similar algorithm to @Marvey and many other reviewers on SBAF. Also, it cost me quite a few vacation days, plus some fuel, to listen to all these.

It's not going to impress anyone who's been around Hi-Fi for a while. It's decent competitor to a computer soundcard and that's about it. Anything similarly priced from schiit is likely going to kill it dead.